The present invention relates to control systems for internal combustion engines, and more particularly to control systems for compensating throttle area of a throttle body.
Electronic throttle control (ETC) systems replace the mechanical pedal assemblies that are currently used in vehicles. ETC systems enhance overall engine management while reducing the cost of the vehicle. Traditional engine controls rely on direct input from drivers and numerous valves and linkages to manage the engine. These systems do not allow consistent throttle control.
ETC sensors eliminate the linkage that is used to connect the accelerator pedal to the throttle body. ETC sensors take input from the driver""s foot and send it to an engine control system in real time. The engine control system modulates the air/fuel flow to the engine. Direct control of the engine is shifted from the driver to the engine control system to improve efficiency.
ETC also can be coordinated with the shifting of the transmission, whereas mechanical systems react solely to the torque applied by the engine. Mechanical systems shift under high-load conditions, which may decrease the life of the transmission over time. ETC systems can reduce throttle, shift, and then increase throttle. This approach will increase the life of the transmission.
As throttle body coke deposits build up on a throttle blade/bore during the life of a vehicle, a relationship between pedal position and throttle response may deteriorate. This deterioration can lead to reduced idle quality. Customers experiencing poor idle quality during a warranty coverage period will request service. As a result, the warranty cost of the vehicle increases. Customers experiencing poor idle quality after the warranty coverage period ends will have higher operating costs. Other conditions that may adversely impact throttle response include variations in an airflow breakout region position, dirty air cleaners, and/or non-linearity in throttle position sensors.
A method and apparatus according to the present invention compensates throttle area in an engine control system with an electronic throttle using intake diagnostic residuals. A plurality of tables relate throttle area, breakpoint numbers, flow loss factors and residual values. At least one of the tables is updated based on the intake diagnostic residuals to generate a compensated throttle area.
In other features of the invention, a first table relates throttle area to breakpoint numbers and residual values. A second table relates residual values to flow loss factors. A third table relates flow loss factors to breakpoint numbers. A fourth table relates throttle area to breakpoint numbers.
In another feature of the invention, a desired throttle area is obtained from a pedal position sensor and/or a cruise control. A current throttle area is used to lookup a first breakpoint number in the first table. The first breakpoint is rounded. An absolute value of a difference between the rounded first breakpoint number and the first breakpoint number is compared to a hysteresis calibration value. The third or fourth tables are updated only when the absolute value is less than the hysteresis calibration value.
In other features of the invention, a current residual value is obtained from an intake diagnostic. Based on the current residual value, a flow loss factor is obtained from the second table. Using the rounded first breakpoint number, a flow loss factor is obtained from the third table. A filtered flow loss factor is calculated from the flow loss factors of the second and third tables. The filtered flow loss factor is stored in the third table in a position corresponding to the rounded first breakpoint number.
In still other features, a clean throttle area is obtained from the first table using the rounded first breakpoint number. The filtered flow loss factor is multiplied by the clean throttle area to provide a product. The fourth table is updated with the product in a position corresponding to the rounded first breakpoint number.
In still other features, a compensated breakpoint number is obtained from the fourth table based on the desired throttle area. A compensated throttle area is obtained from the first table using the compensated breakpoint number.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.